The Selections On Olfactory Receptor Genes, IGF1and MSTN In Dogs

Domestic animals have always been the major issue in genetics. Because of their clear genetic backgrounds, controllable living conditions, the domestic animals have been the model organisms in the genetic research. Domestic dog (Canis lupus familiaris) is the first animal that has been domesticated by human, it has experienced two bottlenecks in its history, accompanying with two important periods under stress of artificial selection, the first is domestication, the second is breed formation. So the dog is a very good pattern animal for our understanding of the genetics of domestic animals. We began with two very important genetic characters of the dog, compared with gray wolf (Canis lupus). We found that how the artificial selection and natural selection effected the dog, and the difference between artificial selection and natural selection.1. The appearance of dog-specific polymorphisms in insulin like growth factor1(IGF1) and myostatin (MSTN)The dog has widest diversity of body size in the mammals, and this diversity is mostly between breeds. It has been found that the body size is associated with a SNP in IGF1, the small dog’s genotype of IGF1is mutated genotype. MSTN is a protein that can affect the growth of muscle. In some domestic animals and human, it has been found that inactivation of this gene encoded this protein can change the phenotypes. However, inactivation of this gene has only been found in whippet. We investigated the Chinese village dog (CVD), and found that the two mutated genotypes appeared in the different period of the dog history, the mutated genotype of IGF1came out before breed formation, while the mutated genotype of MSTN came out after breed formation. In the further analysis, we found that the frequency of mutated genotype in IGF1was associated with the coldest month average temperature, it suggested that the dog was under both artificial selection and natural selection in its history. When the coldest month average temperature is8.4℃, both alleles have the same fitness, it also suggests that the small dog’s allele may originate in tropical area.2. Selections in the olfactory receptor genes in the dogOlfactory receptor gene family is the biggest gene family in mammals, it is constituted by more than one thousand genes. It has been found that acquisition of trichromatic vision caused degeneration of olfactory receptor gene families in primate. The dog and wolf have sensitive olfactions, but the dog has been in the artificial environment for more than ten thousand years. Base on the research of segregating olfactory receptor pseudogenes in dog and wolf, we found that the segregating olfactory receptor pseudogenes had a trend to conserve beneficial mutation and reduce deleterious mutation in the wolf, however, were nearly neutral in the Chinese village dog, under strong artificial selection in breed dogs. We also found that natural selection and artificial selection were completely different.In our investigation, we found that the selection varied in different period, the natural selection played an important role, even in artificial environment. We also found that selection could affect the birth and death of genes, and the difference between artificial selection and natural selection.